Reinforcing support structure



R. M. MARSHALL ET AL June 24, 1969 3,451,452

REINFOHCING SUPPORT STRUCTURE Filed July 26, 1967 Sheet limb W 1. 11M V L 5 f 92 9o 66 62 68 so 86 'Fig. 6

INVENTORS. Roberf M Marsha/l Roberf W Wiffebor/ MM add... PM {QM THE/R A 7' TOR/V5 YS 3,451,452 REINFORCING SUPPORT STRUCTURE Robert M. Marshall and Robert W. Wittebort, Pittsburgh, Pa., assignors to Allegheny Plastics, Inc., Coraopolis, Pa., a corporation of Pennsylvania Filed July 26, 1967, Ser. No. 656,161 Int. Cl. B65d 25 /20, 25/00 US. Cl. 150--0.5 8 Claims ABSTRACT OF THE DISCLOSURE This application relates to a support structure, particularly to a multiple tubular support for reinforcing tank walls and covers formed of plastic or other semirigid flexible material. The structure incorporates novel connections at the tank corners to accommodate expansion and contraction of the tank in response to temperature differentials of the contents of the tank.

Heretofore, it has been customary to use steel or other metal material protected by rubber or lead for the walls, bottom and covers of large tanks, such as tanks for pickling, cleaning etc., used in the production of steel. The reasons for this were twofold: (1) the tanks are required to hold large volumes of liquid, which exert great pressure upon the tank walls and the bottom and, therefore, require materials having high strength, such as steel; and (2) these liquids are often acids, in nearly concentrated form, which tend to corrode and destroy the metals which are not protected in a very short time. Recently, the widespread use of I-ICL for pickling has made it extremely difficult to control corrosion. Moreover, metal tanks require strong, thick foundations, which are expensive to construct, and are substantially immovable, once positioned, except with the use of heavy equipment, such as overhead cranes and the like.

Now, semirigid flexible materials, particularly thermoplastic materials, such as polypropylene, polyvinylchloride and polyethylene are available which have the required anti-corrosive qualities for use in making such tanks. In addition, the strength of the thermoplastics, particularly polypropylene, is sufficient such that self-supporting walls of the tank can be constructed of this material and, therefore, polypropylene tanks can be made in very large sizes: for example, they may be 20 feet long and 10 feet Wide by 10 feet high such that their volume capacity is 2000 cubic feet of liquid. It is obvious, however, that such a tank made of a thermoplastic material, when filled with large volumes of liquid, even at ambient temperature, which will exert a great pressure against the inside of the walls of the tank and tend to push them out, will cease to be self-supporting when the liquids are at high temperatures. Heating to elevated temperatures adversely affects the strength of thermoplastics tending to cause them to sag, buckle and fail, thus destroying the tank and allowing its contents to escape. One method of support used heretofore has been to construct a double tank wall structure which includes inner and outer walls (the latter being of steel) which are spaced to provide a gap which is filled with a liquid of medium sutficient to apply pressure to the outside of the inner wall (formed of plastic material) and thus counteract the pressure from the useful liquid United States Patent in the main tank, While such a construction overcomes the corrosion problem, it is apparent that such a structure not only requires more material for tank construction, but does not fully accomplish the object in that the outer wall still must be made of a substantial material such as metal. A double walled structure, therefore requires much more material and is consequently more expensive than a single plastic-walled tank.

Our invention is a reinforcing structure which is useful in conjunction with a plastic-walled tank and enables the tank to remain self-supporting, under conditions of load and elevated temperature, yet which requires a minimum amount of additional construction material. Briefly, our invention comprises a multiple tubular structure which is adapted to be placed adjacent an outer wall of a plasticwalled tank. Each tube of the structure is formed from a plastic casing in which is loosely inserted a metal pipe. In position adjacent a wall of the tank, an edge of the casing abuts the surface of the wall it is adapted to support. The ends of the tube are plugged to prevent foreign and aggressive materials from attacking the metal pipe.

A multiple tubular structure can also be used to provide rigid support to a bottom of or a cover for the tank, by extending the tubes under and against the tank bottom, or beneath the cover, respectively. In one embodiment, we have provided a novel corner connection whereby two tubular supports are resiliently joined at right angles at a tank corner to accommodate dimensional changes of the tank, i.e., expansion and contraction of the tank walls, in response to changes in tank wall temperature due to variations in temperature of the liquid contents of the tank.

A clearer understanding of our invention will be obtained from the following specification and accompanying drawings of our invention in which:

FIG. 1 is a perspective view of a tank, in the shape of a rectangular prism, incorporating the preferred form of our support structure.

FIG. 2 is an enlarged, broken sectional view taken on the plane 11 in the direction of the arrow II of FIG. 1.

FIG. 3 is a plan view of a tank in the shape of a rectangular prism including a cover member and showing our novel support structure.

FIG. 4 is a sectional view of a portion of the cover of FIG. 3 taken along the lines IVIV of FIG. 3.

FIG 5 is an enlarged section through a connection of one tube of our reinforcing structure to a. tank wall.

FIG. 6 is an enlargement of the inset VI of FIG. 1 and is taken along a horizontal plane through the connection.

Referring to FIG. 1, we have shown a tank 10' in the shape of a rectangular prism. The tank comprises side walls 12 and end walls 14. A rim 16 extends around the top of the tank and is adapted to mate with a tank cover (not shown in FIG. 1). Vertical ribs 18 are connected to the walls 12, 14 and are spaced therearound. Spaced along the lower end of the side walls and connected to alternate ribs supporting the side walls is a plurality of feet 20 which extend under the tank bottom (also not shown in FIG. 1) to space the tank from a plant floor, Inlet port 22, outlet port 24 and overflow port 26 form communication passages from outside to the inside of the tank and are provided for handling the liquid contents of the tank.

A reinforcing structure in accordance with our invention is shown associated with the tank in FIG. 1. The support comprises a plurality of tubes 28 which extend horizontally across the side and end walls of the tank. Each tube extends through a series of ribs 18 such that that a wall surface across which a tube extends is tangent to the outer surface of such tube. Reinforcing tubes (not shown) also extend across the tank perpendicular to the side walls beneath and adjacent the tank bottom.

At each vertical corner 30 of the tank, the tubes in any one horizontal plane of our structure meet approximately right angles, i.e., as at 32, and the ends of the tubes e.g., 28a and 2811 are connected to each other by a novel corner connection to be described in detail hereinafter in connection with FIG, 6.

Viewed from an end of the tank along line II of FIG. 1, our novel structure appears as shown in FIG. 2. Each reinforcing tube 28 comprises a central pipe 36, made of steel or other metal having strength under elevated temperature conditions. The pipe 36 is inserted loosely into a casing 38 made of plastic material and having resistance to corrosion. The pipe 36 is free to slip longitudinally within the casing 38, the clearance provided being on the order of .020. We prefer to use polypropylene plastic as the casing material. The tubes 28 are positioned along a tank wall such that the outer surface of the wall is tangent to a line on the periphery of the pipe which is against the wall surface.

A bottom 40 of the tank, shown in FIG. 2, is also supported by a plurality of spaced tubes 28 comprising a metal pipe 36 inserted within a polypropylene casing 38. The tubes extend between the side walls 12 and are located such that the bottom 40 of the tank rests on the upper edge of a, series of tubes 28. The tubes are retained and themselves encased in the side walls 12 in the manner shown in FIG. 5.

As pointed out earlier, the tanks to which our invention is especially applicable often are found in steel-making plants, where as part of the processing, acid baths such as HCl and H 50 are commonly used. It is particularly important that such tanks, therefore, be provided with a means of closure so that workmen near the tank will not be exposed to the acid fumes and/or spray emanating from the tank. Moreover, workmen moving from one area to another in a plant often work above the tanks and walk near the tank rim, Hence, some means of protection must be provided to prevent one from slipping or falling into the tank.

We have provided such a tank closure means in the form of a reinforced tank cover 42 which is shown in FIGS. 3 and 4. While covers per se are known, our cover incorporates the novel features of our reinforcing structure.

Specifically, in FIGS. 3 and 4, there is shown a cover 42 comprising a top wall 44 which slopes from the center of the tank toward the tank rim at each end wall 14. A lip 46 extends from the edge of the top wall substantially vertically to attach to the tank rim 16. The method of attachment of the cover lip 46 of the tank walls 12, 14 may be either overlap or underlap, both types of connections recently being used.

Lifting lugs 48, four of which are shown in FIG. 3, connected to the top wall 44 of the cover, form means by which the cover may be raised and removed from the tank by crane or other equipment. Resting pads 50 are located at the ends of the cover and provide means for stocking of a number of covers, one on top of the other, when removed from a tank.

Our novel reinforcing structure for the cover comprises a plurality of tubes 28 each of which includes a metal pipe 36 covered with a plastic casing 38. The tubes are mounted such that the bottom surf-ace of the top wall 44 of the cover is tangent to the outer surface of the casing 38. This is accomplished by connecting the tubes into the depending lip 46 of the cover in the manner such as is illustrated in FIG. 5.

A method of connecting and mounting a tube 28 including a metal pipe 36 having a plastic casing 38 therearound is shown in FIG. 5. A hole 52 of substantially the same diameter as the outer diameter of the casing is drilled in a straight wall W, which may be one of the end and side walls 14, 12 of a tank, or a depending lip 46 of the cover. The metal pipe 36 within the casing 38 does not extend the full length of the casing. A plastic plug 54, which may also be made of polypropylene, is

inserted into the end of the plastic casing 38 and welded to the casing along the circumference of the plug 54. Accordingly, the metal pipe is sealed against corrosive liquids entering the support structure. The tube 28 is then inserted into the hole to a point such that the end of the plasic casing 38 is flush with or inside the outer surface of the wall W. The tube end is then welded to the wall at 55 along its circumference.

Plastic has a coefficient of expansion which is greater than metal, and polypropylene, in particular, has a coeflicient of expansion about 6 times that of steel. We have found that, when low temperature liquid contents are used in a tank having our support, the polypropylene tube casing contracts in response to the decreased temperature of the tank structure substantially more than does the metal pipe within it. Hence, the metal pipe tends to blow or force the plug 54 out of the end of the casing. To overcome this, our connection, as shown in FIG. 5, can be modified by placing, before closing the end of the casing with the plug, a thin foam plastic cap 58, which may be also made of polypropylene, having a diameter about the same as the outer diameter of the metal pipe 36 against the end of the metal pipe.

When the polypropylene casing contracts causing the plug 54 to contract with it, the foam cap 58 is compressed between the plug and the end of the steel pipe 36 and absorbs the force of the pipe with little or very little force being transmitted to the plug.

An alternate method to FIG. 5 of retaining a tube in position between a pair of parallel straight walls, such as either walls 12, 14 or opposed lips 46 is to afiix on the inside thereof a flat plastic plate which is larger than the section of a tube 38. A hole of substantially the same diameter as the casing of the tube is located in the plate and extends through the wall. The tube, having an inner steel pipe, is inserted into the hole and extends such that the outer end of the plastic casing is within the inner surface of the plate. A polypropylene plug, similar to plug 54, is inserted into the end of the casing and a weldment made to fill the hole in the wall closing the hole end sealing the metal pipe against aggressive elements.

It is understood that temperature changes of the liquid contents of tanks, such as that described herein, cause the tank walls to expand and contract. Tanks made of plastic material, in view of the large coefiicient of expansion of plastic, are subject to large dimensional changes and it is important to accommodate these changes in any reinforcing structure. We have invented a novel corner connection for our structure for this purpose.

As shown in FIG. 6, a tank end wall 14 is connected to a tank side wall 12 in a corner connection 56. Tubes 58 and 60 made in accordance with our teaching, are tangent to a line along their respective walls, running in the direction of the tubes. End 62 of tube 60 is approximately flush with outer surface 64 of wall 12 and is formed such that plastic casing 66 of pipe 60 abuts casing 68 of tube 58 substantially the whole way around its end when positioned. Metal pipe 70 is fitted with a plug 72 which is welded at 74 before abutting tubes 58 and 60. Plug 72 has a central threaded hole 78.

End of pipe 81 is provided with apertures 82 and 84 which are aligned with hole 78 in plug 72. Bolt 86 inserted through the apertures in tube 58 is threaded into hole 78 aligned with the longitudinal axis of pipe 60. A coil spring 88 disposed between washers 90 and 92 and upon bolt 86 between its head 76 and tube 58 biases tube 60 against tube 58. Hence, the tubes 58 and 60 are free to move relative to one another as the support structure expands and contracts due to temperature change of the walls in response to temperature change of the liquid contents of the tank.

Similar corner connections are provided at each of the four corners of the tank; however, the bolt connecting the opposite end of pipe 58 to that pipe running parallel with pipe 60 along the opposed side wall of the tank (not shown in FIG. 6) is aligned with the longitudinal axis of pipe 58. Hence, each tube of length substantially equal to the length of the wall it supports in a single horizontal plane is offset from such Wall a distance approximately equal to the casing diameter of the tube to which it is connected. Such a corner connection, We have found, permits the tank walls to expand and contract in response to temperature variations as required, without destroying either the tube structure or the welded ends and plugs. To protect the otherwise exposed metal bolts and washers from corrosion, they may be suitably coated with polypropylene or other plastic compositions.

Our invention permits low cost materials to be used in the construction of large tanks for industrial use. The support structure further permits expansion and contraction of the tank in response to the temperature differentials of the contents, thereby not limiting the uses to which the tank can be put. Furthermore, the cover structure, when utilized in connection with the tank, will support the weight of a man who may wish to cross it.

Throughout we refer to a support member comprising a metal pipe freely mounted in a tubular casing. Also, within our contemplation is a support member comprising a metal bar or I-beam construction which is loosely mounted in a casing having a rectangular, square or other cross section generally conforming to the shape of the bar or beam.

We claim:

-1. A reinforcing structure comprising:

(A) a wall of semirigid material and having spaced means thereon for mounting a support member adjacent the wall to support the wall against loss of strength due to temperature variation;

(B) at least one tube support member including a semirigid closed casing member extending across said wall and a length of metal pipe freely mounted within the casing and extending substantially therethrough; and

(C) said tube support member extending through said spaced mounting means, a surface of the tube support member contacting a surface of the wall substantially tangentially to support the wall under conditions of temperature variation.

2. The structure of claim 1 wherein a plurality of tube support members are located along the wall, each support member extending through the spaced mounting means such that the support members are substantially parallel to one another.

3. A reinforcing structure as set forth in claim 1 in which the casing is closed by a plastic plug secured in an end thereof to prevent communication of foreign matter with the pipe.

4. A reinforcing structure as set forth in claim 3 and including a foam plastic cap member disposed between an end of the pipe and the plug and within the casing.

5. A reinforcing structure for a tank comprising:

(A) at least two semirigid walls perpendicularly positioned to form a corner of the tank;

(B) spaced means on each of the walls for mounting a support member adjacent to the wall to support the Wall against loss of strength;

(C) at least one tube support member including a semirigid closed casing extending across each wall and a length of metal pipe freely mounted within the casing and extending substantially therethrough;

(D) each tube support member extending in substantially the same plane and through the spaced mounting means of the wall it is to support such that an end of one tube support member is adjacent an end of another such member, a surface of each tube support member contacting a surface of such wall substantially tangentially thereof; and

(E) means for resiliently connecting the adjacent ends of the members to one another.

6. The structure of claim 5 wherein the resilient connection means comprises:

(A) an end of a first support member being abutted against the side of a second support member near an end thereof and extending at right angles thereto;

(B) a bolt extending laterally through. said second support member and substantially axially coextensive with said first support member;

(C) said first support member having means in an end thereof for connecting to said bolt; and

(D) spring means on the bolt between a head thereof and said second support member for resiliently biasing said second support member into abutment with said first support member and responsive to dimensional changes of said support members relative to one another.

7. In a plastic cover for a tank, a reinforcing structure comprising:

(A) a top wall of semirigid material and having spaced means thereon for mounting a support member adjacent the top Wall to support the wall;

(B) at least one tube support member including a semirigid closed casing member extending across the top wall and a length of metal pipe freely mounted within the casing and extending substantially therethrough; and

(C) said tube support member extending through the spaced mounting means, a surface of the tube support member contacting a surface of the top wall substantially tangentially to support the top wall.

8. A reinforcing structure as set forth in claim 7 in which the spaced mounting means compirse parallel flanges depending from opposed edges of the top wall.

References Cited UNITED STATES PATENTS 3,337,086 8/ 1967 Jenks 22O6 3 3,148,798 9/1964 Brown 22042 3,265,240 8/1966 Cloyd 220-84 3,115,982 12/1963 Morrison 2201.5

GEORGE E. LOWRANCE, Primary Examiner.

US. Cl. X.R. 220-71, 84 

